Cytomegalovirus (CMV) infection is the most common infection that occurs after renal transplantation. It is a significant cause of morbidity and even mortality after transplantation and has been linked with graft rejection. Heretofore, only serum antibody has been used to assess immunity to CMV in prospective studies of transplant patients. However, serologic studies frequently have not been helpful in determining who is at risk for developing CMV infection nor has seroconversion necessarily been correlated with recovery nor failure to seroconvert with failure to recover. This finding may not seem surprising, since experimental and clinical data suggest that cell-mediated immunity is a more important host defense than humoral immunity for CMV and the other herpesviruses. No systematic prospective studies of cell-mediated immunity to CMV in renal transplant recipients have thus far been reported. While preliminary studies have found a good correlation between serum antibody and cell-mediated immunity in normal subjects, no such correlation has been found in transplant recipients. Our objective in the studies in this proposal is to examine cell-mediated immunity to CMV in renal transplant recipients and to relate cell-mediated immunity to serum antibody, to CMV shedding, immunosuppression, and illness due to CMV infection. We will do this by serially determining humoral antibody and cell-mediated immunity to CMV when patients in end-stage renal disease present for renal transplantation. These tests will be determined frequently on these patients following transplantation. The patients will also be followed closely so that we can relate the immune status to CMV to the patients' clinical status. We will determine serum antibody by complement-fixing and immunofluorescence antibody tests. Cell-mediated immunity will be determined by 3H-thymidine incorporation by peripheral blood T lymphocytes in response to CMV antigen. Responses to herpes simplex virus antigen phytohemagglutinin, and concanavallin A will serve as controls. This study may demonstrate that tests of cell-mediated immunity to CMV provides more helpful information in determining who is most at risk for CMV infection and the eventual outcome of that infection.